Refactor to introduce a main method

Also, added a unit test.
Signed-off-by: NNadeem Ghani <nghani@pivotal.io>

gpMgmt/bin/gppylib/test/unit/test_unit_gpssh.py

+import imp
+import os
+import io
+
+import sys
+from mock import patch
+
+from gp_unittest import GpTestCase
+
+
+class GpSshTestCase(GpTestCase):
+
+    def setUp(self):
+        # because gpssh does not have a .py extension, we have to use imp to import it
+        # if we had a gpssh.py, this is equivalent to:
+        #   import gpssh
+        #   self.subject = gpssh
+        gpssh_file = os.path.abspath(os.path.dirname(__file__) + "/../../../gpssh")
+        self.subject = imp.load_source('gpssh', gpssh_file)
+
+    @patch('sys.exit')
+    def test_when_run_without_args_prints_help_text(self, mock):
+        mock.side_effect = Exception("on purpose")
+        # GOOD_MOCK_EXAMPLE of stdout
+        with patch('sys.stdout', new=io.BytesIO()) as mock_stdout:
+            with self.assertRaisesRegexp(Exception, "on purpose"):
+                self.subject.main()
+        # assert on what main() was expected to do
+        # in this case, check what was written to sys.stdout?
+        self.assertIn('gpssh -- ssh access to multiple hosts at once', mock_stdout.getvalue())
+
+    def test_when_remote_host_cpu_load_causes_bad_prompts_will_retry_and_succeed(self):
+        pass
+        # sys.argv = ['', '-h', 'localhost', 'uptime']
+        # self.subject.main()
+        # assert on what main() was expected to do
+        # in this case, check what was written to sys.stdout?
+
+    def test_when_remote_host_cpu_load_causes_bad_prompts_will_retry_and_fail(self):
+        pass
+        

gpMgmt/bin/gpssh

@@ -19,14 +19,9 @@ Usage: gpssh [--version] [-?v] [-h host] [-f hostfile] [cmd]
 import os
 import sys
 
-progname = os.path.split(sys.argv[0])[-1]
+# todo is this necessary?
 sys.path.insert(1, sys.path[0] + '/lib')
 
-if sys.version_info < (2, 5, 0):
-    sys.exit(
-'''Error: %s is supported on Python versions 2.5 or greater
-Please upgrade python installed on this machine.''' % progname)
-
 import getopt
 import atexit
 import signal
@@ -69,13 +64,11 @@ def usage(exitarg):
     sys.exit(exitarg)
 
 
-#############
 def print_version():
     print '%s version $Revision$' % GV.script_name
     sys.exit(0)
 
 
-#############
 def parseCommandLine():
     try:
         (options, args) = getopt.getopt(sys.argv[1:], '?evsh:f:D:u:d:t:', ['version'])
@@ -224,52 +217,63 @@ def interactive():
             pass
 
 
-try:
-    # Parse options from the command line
-    parseCommandLine()
-
-    # Parse gpssh.conf file
-    parseConfigFile()
-
-    # Acquire the list of hosts from command line arguments
-    hostlist = ssh_utils.HostList()
-    for h in GV.opt['-h']:
-        hostlist.add(h)
-    if GV.opt['-f']:
-        hostlist.parseFile(GV.opt['-f'])
+def main():
+    if sys.version_info < (2, 5, 0):
+        sys.exit(
+            '''Error: %s is supported on Python versions 2.5 or greater
+            Please upgrade python installed on this machine.''' % os.path.split(sys.argv[0])[-1])
 
-    # Filter out non-unique hostnames unless the -D option is provided
-    if not GV.opt['-D']:
-        GV.opt['-h'] = hostlist.filterMultiHomedHosts()
-    else:
-        GV.opt['-h'] = hostlist.get()
+    try:
+        # Parse options from the command line
+        parseCommandLine()
+
+        # Parse gpssh.conf file
+        parseConfigFile()
+
+        # Acquire the list of hosts from command line arguments
+        hostlist = ssh_utils.HostList()
+        for h in GV.opt['-h']:
+            hostlist.add(h)
+        if GV.opt['-f']:
+            hostlist.parseFile(GV.opt['-f'])
+
+        # Filter out non-unique hostnames unless the -D option is provided
+        if not GV.opt['-D']:
+            GV.opt['-h'] = hostlist.filterMultiHomedHosts()
+        else:
+            GV.opt['-h'] = hostlist.get()
+
+        if len(GV.opt['-h']) == 0:
+            usage('Error: missing hosts in -h and/or -f arguments')
+
+        # If a single command was passed to us, implement a single command session
+        if GV.argcmd:
+            try:
+                GV.session = ssh_utils.Session()
+                GV.session.verbose = GV.opt['-v']
+                GV.session.login(GV.opt['-h'], GV.USER, GV.DELAY_BEFORE_SEND, GV.PROMPT_VALIDATION_TIMEOUT)
+                GV.session.echoCommand = GV.opt['-e']
+                if GV.opt['-s']:
+                    GV.session.executeCommand("source {0}/greenplum_path.sh".format(os.environ["GPHOME"]))
+                output = GV.session.executeCommand(GV.argcmd)
+                GV.session.writeCommandOutput(output)
+                if GV.session.verbose: print '[INFO] completed successfully'
+                sys.stdout.flush()
+            except ssh_utils.Session.SessionError, e:
+                print 'Error: %s' % e
+                pass
 
-    if len(GV.opt['-h']) == 0:
-        usage('Error: missing hosts in -h and/or -f arguments')
+        else:  # Otherwise, implement an interactive session
+            interactive()
 
-    # If a single command was passed to us, implement a single command session
-    if GV.argcmd:
-        try:
-            GV.session = ssh_utils.Session()
-            GV.session.verbose = GV.opt['-v']
-            GV.session.login(GV.opt['-h'], GV.USER, GV.DELAY_BEFORE_SEND, GV.PROMPT_VALIDATION_TIMEOUT)
-            GV.session.echoCommand = GV.opt['-e']
-            if GV.opt['-s']:
-                GV.session.executeCommand("source {0}/greenplum_path.sh".format(os.environ["GPHOME"]))
-            output = GV.session.executeCommand(GV.argcmd)
-            GV.session.writeCommandOutput(output)
-            if GV.session.verbose: print '[INFO] completed successfully'
-            sys.stdout.flush()
-        except ssh_utils.Session.SessionError, e:
-            print 'Error: %s' % e
-            pass
+        return_code = sessionCleanup()
+        sys.exit(return_code)
 
-    else:  # Otherwise, implement an interactive session
-        interactive()
+    except KeyboardInterrupt:
+        sessionCleanup()
+        sys.exit('\nInterrupted...')
 
-    return_code = sessionCleanup()
-    sys.exit(return_code)
 
-except KeyboardInterrupt:
-    sessionCleanup()
-    sys.exit('\nInterrupted...')
+#############
+if __name__ == '__main__':
+    main()